Mixed metal oxide catalysts for the production of unsaturated aldehydes from olefins

ABSTRACT

A catalyst for production of unsaturated aldehydes, such as methacrolein, by gas phase catalytic oxidation of olefins, such as isobutylene, contains oxides of molybdenum, bismuth, iron, cesium and, optionally, other metals. The catalyst has a certain relative amount ratio of cesium to bismuth, a certain relative amount ratio of iron to bismuth and a certain relative amount ratio of bismuth, iron, cesium and certain other metals to molybdenum and, optionally, tungsten. For a catalyst of the formula:
 
Mo 12 Bi a W b Fe c Co d Ni e Sb f Cs g Mg h Zn i P j O x 
 
wherein a is 0.1 to 1.5, b is 0 to 4, c is 0.2 to 5.0, d is 0 to 9, e is 0 to 9, f is 0 to 2.0, g is from 0.4 to 1.5, h is 0 to 1.5, i is 0 to 2.0, j is 0 to 0.5 and x is determined by the valences of the other components, c:g=3.3–5.0, c:a=2.0–6.0 and (3a+3c+2d+2e+g+2h+2i)/(2×12+2b)=0.95–1.10.

This is a continuation-in-part application of application Ser. No.10/403,213 filed Mar. 31, 2003, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a mixed metal oxide catalyst containing oxidesof molybdenum, bismuth, iron, cesium and, optionally, other metals forthe production of unsaturated aldehydes from olefins, such asmethacrolein by gas phase catalytic oxidation of isobutylene in thepresence of air or another gas containing molecular oxygen.

2. Description of the Prior Art

Many catalysts have been disclosed for use in the production of acroleinor methacrolein by catalytic vapor phase oxidation of propylene orisobutylene. U.S. Pat. No. 4,816,603 discloses a catalyst for productionof methacrolein and methacrylic acid of the formula:Mo_(a)W_(b)Bi_(c)Fe_(d)Ni_(e)Sb_(f)X_(g)Y_(h)Z_(i)A_(j)O_(k)where X is potassium, rubidium and/or cesium, Y is phosphorus, sulfur,silicon, selenium, germanium and/or boron, Z is zinc and/or lead, A ismagnesium, cobalt, manganese and/or tin, a is 12, b is 0.001 to 2, c is0.01 to 3, d is 0.01 to 8, e is 0.01 to 10, f is 0.01 to 5, g is 0.01 to2, h is 0 to 5, i is 0.01 to 5, j is 0 to 10 and k is sufficient tosatisfy the valences.

U.S. Pat. No. 4,511,671 discloses a catalyst for manufacturingmethacrolein of the formula:Mo_(a)W_(b)Bi_(c)Fe_(d)A_(e)B_(f)C_(g)D_(h)O_(x)where A is at least one of nickel and/or cobalt; B is at least one ofalkali metals, alkaline earth metals and/or thallium; C is at least oneof phosphorus, tellurium, antimony, tin, cerium, lead, niobium,manganese and/or zinc; D is at least one of silicon, aluminum,zirconium, and/or titanium; a is 12, b is 0 to 10, c is 0.1 to 10, d is0.1 to 20, e is 2 to 20, f is 0 to 10, g is 0 to 4, h is 0 to 30 and xis determined by the atomic valences.

U.S. Pat. No. 4,556,731 discloses a catalyst for production ofmethacrolein and methacrylic acid of the formula:A_(a)B_(b)Fe_(c)X_(d)M_(e)Mo₁₂O_(x)where A is an alkali metal, such as potassium, rubidium, cesium ormixtures thereof, thallium, silver or mixtures thereof, B is cobalt,nickel, zinc, cadmium, beryllium, calcium, strontium, barium, radium ormixtures thereof, X is bismuth, tellurium or mixtures thereof and M is(1) Cr+W, Ge+W, Mn+Sb, Cr+P, Ge+P, Cu+W, Cu+Sn, Mn+Cr, Pr+W, Ce+W,Sn+Mn, Mn+Ge or combinations thereof, (2) Cr, Sb, Ce, Pn, Ge, B, Sn, Cuor combinations thereof, or (3) Mg+P, Mg+Cu, Mg+Cr, Mg+Cr+W, Mg+W, Mg+Snor combinations thereof, a is 0 to 5, b is 0 to 20, c is 0 to 20, d is 0to 20, e is 0.01 to 12 and x satisfies the valence requirements.

U.S. Pat. No. 5,245,083 discloses a catalyst for preparing methacroleinof a mixture of composition (1) of the formula:Mo_(a)Bi_(b)Fe_(c)X_(d)Z_(f)O_(g)where X is Ni and/or Co, Z is at least one of W, Be, Mg, S, Ca, Sr, Ba,Te, Se, Ce, Ge, Mn, Zn, Cr, Ag, Sb, Pb, As, B, P, Nb, Cu, Cd, Sn, Al, Zrand Ti, a is 12 b is 0.1 to 10, c is 0 to 20, d is 0 to 20, f is 0 to 4and g satisfies the valence requirement and composition (2) of theformula:A_(m)Mo_(n)O_(p)where A is at least one of K, Rb and Cs, m is 2, n is 1 to 9 and p is3n+1.

U.S. Pat. No. 5,138,100 discloses a catalyst for preparing methacroleinwith a mixture of composition (1) of the formula:Mo_(a)Bi_(b)Fe_(c)X_(d)Y_(e)Z_(f)O_(g)where X is at least one of Ni and Co, Y is at least one of K, Rb, Cs andTi, Z is at least one of the elements belonging to Groups 2, 3, 4, 5, 6,7, 11, 12, 13, 14, 15 and 16, specifically beryllium, magnesium,calcium, strontium, barium, titanium, zirconium, cerium, niobium,chromium, tungsten, manganese, copper, silver, zinc, cadmium, boron,aluminum, germanium, tin, lead, phosphorus, arsenic, antimony, sulfur,selenium and tellurium, a is 12, b is 0.1 to 10, c is 0 to 20, d is 0 to20, e is 0 to 2, f is 0 to 4, and g satisfies the valence requirementand composition (2) of the formula:Ln_(h)Mo_(i)O_(j)where Ln is at least one of the rare earth elements, h is 0.2 to 1.5, iis 1 and j satisfies the valence requirement. The atomic ratio of therare earth element to molybdenum is disclosed to be in the range from0.2 to 1.5 with an atomic ratio less than 0.2 resulting in highselectivity but poor activity and with an atomic ratio greater than 1.5resulting in high activity but poor selectivity.

U.S. Pat. No. 4,537,874 discloses a catalyst for production ofunsaturated aldehydes of the formula:Bi_(a)W_(b)Fe_(c)Mo_(d)A_(e)B_(f)C_(g)D_(h)O_(x)where A is nickel and/or cobalt, B is at least one of alkali metal,alkaline earth metals and thallium, C is at least one of phosphorus,arsenic, boron, antimony, tin, cerium, lead and niobium, D is at leastone of silicon, aluminum, zirconium and titanium, a is 0.1 to 10.0, b is0.5 to 10.0, c is 0.1 to 10.0, d is 12, e is 2.0 to 20.0, f is 0.001 to10.0, g is 0 to 10.0 and h satisfies the valence requirement. The ratioof a/b is 0.01 to 6.0 so that bismuth is combined very stably withtungsten and compounds such as bismuth trioxide and bismuth molybdateare not formed.

U.S. Pat. No. 5,728,894 discloses a catalyst for producing methacroleinof the formula:Mo₁₂Bi_(a)Ce_(b)K_(c)Fe_(d)A_(e)B_(f)O_(g)where A is Co or a mixture of Co and Mg having an atomic ratio of Mg toCo not more than 0.7, B is Rb, Cs or a mixture thereof, a is 0 to 8, bis 0 to 8, c is 0 to 1.2, d is 0 to 2.5, e is 1.0 to 12, f is 0 to 2.0,g satisfies the valence requirement. The relative atomic ratio of ironto bismuth and cerium should be 0<d/(a+b+d)≦0.9. The relative atomicratio of bismuth, cerium and potassium should be 0.05≦b/(a+b+c)≦0.7. Therelative atomic ratio of potassium to bismuth and cerium should be0<c/(a+b+c)≦0.4. Bismuth, cerium, potassium, iron and cobalt areindispensable elements for the disclosed invention.

U.S. Pat. No. 5,166,119 discloses a method for preparing a catalyst ofmolybdenum, bismuth, iron and cesium or thallium for producingmethacrolein and methacrylic acid by gas phase catalytic oxidation ofisobutylene or tert-butanol with molecular oxygen. There is nopreference disclosed of cesium over thallium.

Prior art discloses mixed metal oxide catalysts which containmolybdenum, bismuth, iron, cesium and other metals for the production ofmethacrolein. Furthermore, prior art discloses certain ranges of amountsof these metals. Some prior art discloses relative ratios of certaincomponents to other components. The effect of the selection of certaincomponents for a mixed metal oxide catalyst for the production ofmethacrolein and the relative relationship of some of these componentsto other components has not been investigated in complete detail.

SUMMARY OF THE INVENTION

The present invention is for a catalyst of the general formula:Mo₁₂Bi_(a)W_(b)Fe_(c)Cs_(g)M_(m)O_(x)wherein a is in the range from 0.1 to 1.5, b is in the range from 0 to9, c is in the range from 0.2 to 5.0, g is in the range from 0.1 to 1.5,M is one or more selected from calcium, strontium, lithium, sodium,selenium, cobalt, nickel, magnesium, zinc, potassium, rubidium,thallium, manganese, barium, chromium, tin, lead, cadmium and copper, mis in the range from 0 to 9, x is determined by the valences of theother components. Other components, such as cerium, antimony,phosphorus, boron, sulfur, silicon, aluminum, titanium, tellurium,vanadium, zirconium and niobium may also be present. The catalyst of thepresent invention has a relative amount ratio of iron to cesium which isin the range of 3.3 to 5.0, i.e., c:g=3.3–5.0, a relative amount ratioof iron to bismuth which is in the range of 2.0 to 6.0, i.e.,c:a=2.0–6.0 and a relative amount of bismuth, iron and cesium tomolybdenum and tungsten which is in the range of 0.95 to 1.10, i.e.,(3a+3c+g+Σv_(n)m_(n))/(2×12+2b)=0.95 to 1.10 with v being the valence ofeach M, m being the relative amount of each M and n being the totalnumber of M metal(s) present in the catalyst. The process of making thecatalyst is generally to dissolve the metal compounds of molybdenum,bismuth, iron, cesium and, optionally, other metals, such as tungsten,calcium, strontium, lithium, sodium, selenium, cobalt, nickel,magnesium, zinc, potassium, rubidium, thallium, manganese, barium,chromium, tin, lead, cadmium, copper, cerium, antimony, phosphorus,boron, sulfur, silicon, aluminum, titanium, tellurium, vanadium,zirconium and niobium, and precipitate a catalyst precursor which iscalcined to form a mixed metal oxide catalyst. The metal compounds maybe salts (e.g., nitrates, halides, ammonium, organic acid, inorganicacid), oxides, hydroxides, carbonates, oxyhalides, sulfates and othergroups which may exchange with oxygen under high temperatures so thatthe metal compounds become metal oxides. In one embodiment of theinvention, the metal compounds are soluble in water or an acid. Inanother embodiment of the invention the molybdenum compound and thetungsten compound are ammonium salts, the phosphorus compound isphosphoric acid, and that the bismuth compound, the ferric compound, thenickel compound, the cobalt compound, the magnesium compound, the zinccompound, the cesium compound, the potassium compound, the rubidiumcompound, the thallium compound, the manganese compound, the bariumcompound, the chromium compound, the boron compound, the sulfurcompound, the silicon compound, the aluminum compound, the titaniumcompound, the cerium compound, the tellurium compound, the tin compound,the vanadium compound, the zirconium compound, the lead compound, thecadmium compound, the copper compound and the niobium compound arenitrates, oxides or acids and the antimony compound is an oxide.

The process of using the catalyst is generally in a gas phase catalyticoxidation of an olefin to an aldehyde by contacting an olefin, such aspropylene or isobutylene, and a molecular oxygen-containing gas in thepresence of the catalyst of the present invention to form an aldehyde.The use of the catalyst of the present invention in this processincreases activity and selectivity to the production of methacrolein.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

According to the present invention, a catalyst is provided for producingacrolein or methacrolein by oxidation of propylene or isobutylene. Theoxidation is a catalytic reaction that converts an olefin in thepresence of oxygen to an unsaturated aldehyde and water:H₂C═CA-CH₃+O₂->H₂C═CA-CHO+H₂Owhere A is hydrogen or an alkyl group. Carboxylic acid is also producedin a side reaction.

The catalyst is a mixed metal oxide of the formula:Mo₁₂Bi_(a)W_(b)Fe_(c)Cs_(g)M_(m)O_(x)wherein a is in the range from 0.1 to 1.5, b is 0 to 9, c is in therange from 0.2 to 5.0, g is in the range from 0.1 to 1.5, with arelative amount ratio of iron to cesium in the range of 3.3 to 5.0,i.e., c:g=3.3–5.0, and a relative amount ratio of iron to bismuth in therange of 2.0 to 6.0, i.e., c:a=2.0–6.0, M is one or more selected fromcalcium, strontium, lithium, sodium, selenium, cobalt, nickel,magnesium, zinc, potassium, rubidium, thallium, manganese, barium,chromium, tin, lead, cadmium and copper, m is in the range from 0 to 9and x is determined by the valences of the other components, with therelative amount ratio of bismuth, iron, cesium, and any and all M metalsto molybdenum and tungsten represented by the formula(3a+3c+g+Σv_(n)m_(n))/(2×12+2b)=0.95–1.10 wherein Σv_(n)m_(n) is the sumof the product of the valance (v) and the relative amount of each M (m),n being the total number of M metal(s) present in the catalyst. Forexample, if M were nickel (v=2, n=1) and cobalt (v=2, n=2) present inthe amounts of 4.0 and 0.5, respectively, Σv_(n)m_(n) would be(2×4.0)+(2×0.5)=9. In an embodiment of the invention for a catalyst forproducing methacrolein by oxidation of isobutylene, g is in the rangefrom 0.4 to 1.5.

U.S. Pat. No. 5,728,894 discloses three relationships of relative atomicratios:

-   -   iron to bismuth and cerium: 0<d/(a+b+d)≦0.9    -   bismuth, cerium and potassium: 0.05≦b/(a+b+c)≦0.7    -   potassium to bismuth and cerium: 0<c/(a+b+c)≦0.4

The first relationship of relative atomic ratios defines the relativeamount of iron to bismuth. Based on this relationship, the iron contentshould be less than the bismuth content, which can be seen in theexamples of U.S. Pat. No. 5,728,894. The relationship disclosed in thepresent invention is to the contrary in that the iron content is greaterthan the bismuth content, i.e., c:a=2.0–6.0.

The second relationship of relative atomic ratios defines the relativeamount of cerium content. Cerium is not a required element of thecatalyst of the present invention. U.S. Pat. No. 5,728,894 disclosescerium as an indispensable element of this prior art catalyst.

The third relationship of relative atomic ratios defines the relativeamount of alkaline metals in the catalyst to the bismuth content. In thecatalyst of the present invention, the relative amount of alkalinemetals to bismuth is greater than the upper limit disclosed in U.S. Pat.No. 5,728,894 (0.4).

In the catalyst of U.S. Pat. No. 5,728,894, cerium, potassium and cobaltare indispensable elements while in the catalyst of the presentinvention these elements are optional.

In an embodiment of the present invention, the catalyst is of theformula:Mo₁₂Bi_(a)W_(b)Fe_(c)Cs_(g)M_(m)M′_(m′)O_(x)wherein M′ is one or more of cerium, antimony, phosphorus, boron,sulfur, silicon, aluminum, titanium, tellurium, vanadium, zirconium andniobium and m′ is from 0 to 9. M′ and m′ would not be taken into accountin the formulae above for relative amounts of components.

In another embodiment of the invention the catalyst is of the formula:Mo₁₂Bi_(a)W_(b)Fe_(c)Co_(d)Ni_(e)Sb_(f)Cs_(g)Mg_(h)Zn_(i)P_(j)O_(x)wherein b is 0 to 4, d is 0 to 9, e is 0 to 9, f is 0 to 2.0, h is 0 to1.5, c:g is in the range of 3.3–4.8, c:a is in the range of 2.4–4.8, andthe relative amount of bismuth, iron, cesium, cobalt, nickel, magnesium,and/or zinc to molybdenum and tungsten is represented by the formula(3a+3c+2d+2e+2h+2i)/(2×12+2b)=0.95–1.09.

The process of making the catalyst is generally to dissolve the metalcompounds in water or in an acid, precipitate a solid catalyst precursorto form a slurry, separate the solid by removing liquid from the slurryto leave a solid, dry the solid, and calcine the solid to form a mixedmetal oxide catalyst. The metal compounds may be salts (e.g., nitrates,halides, ammonium, organic acid, inorganic acid), oxides, hydroxides,carbonates, oxyhalides, sulfates and other groups which may exchangewith oxygen under high temperatures so that the metal compounds becomemetal oxides. In one embodiment of the invention, the metal compoundsare soluble in water or an acid. In another embodiment of the inventionthe molybdenum compound and the tungsten compound are ammonium salts,such as ammonium paramolybdate or ammonium molybdate and ammoniumparatungstate or ammonium tungstate, respectively, the phosphoruscompound is phosphoric acid, the bismuth, iron, cobalt, nickel, cesium,magnesium, zinc, phosphorus, potassium, rubidium, thallium, manganese,barium, chromium, boron, sulfur, silicon, aluminum, titanium, cerium,tellurium, tin, vanadium, zirconium, lead, cadmium, copper and niobiumcompounds are nitrates, oxides or acids, the antimony compound is anoxide, such as antimony oxide or antimony trioxide, the calcium,strontium, lithium and sodium compounds are nitrates or carbonates andthe selenium compound is an oxide. In one embodiment of the invention,the bismuth, iron, cesium, cobalt, nickel, magnesium and zinc compoundsare nitrates.

The present invention does not depend on a particular order of additionof the components. While a particular order of addition of the variousmetal compound components may affect the performance of the catalyst,the present invention is directed toward the particular relative amountof certain components to other components without regard to the order inwhich the steps in the process of making the catalyst occur.

An example of making the catalyst of the claimed invention is todissolve an ammonium salt of molybdenum, such as ammonium paramolybdateor ammonium molybdate and, optionally, an ammonium salt of tungsten,such as ammonium paratungstate or ammonium tungstate, and phosphoricacid in water, dissolve a bismuth nitrate in an acid, dissolve an ironnitrate and, optionally, a cobalt nitrate, a nickel nitrate, a magnesiumnitrate, and a zinc nitrate in water or in the acid with the bismuthnitrate, mix the solutions at a temperature in the range from 40° C. to100° C., or at 60° C. to 95° C., to obtain a precipitate to form aslurry and then add a cesium nitrate and, optionally, an antimony oxideto the slurry while maintaining the temperature. The cesium nitrate andthe antimony oxide may be added to the slurry as solids. The slurry maybe aged for 2 to 24 hours, for 8 to 18 hours or for 5 to 10 hours. Theliquid of the slurry is removed by evaporation and the solid precipitateis dried and calcined to obtain a catalyst. The liquid may be removedand the solid precipitate dried at the same time by spray drying. Theliquid may be evaporated at a temperature of 50° to 125° C.

Drying of the catalyst precursor may be in air or an inert gas and in anoven or a spray dryer. In one embodiment of the invention, drying is inan oven in air at a temperature of 100–150° C. for 2–5 hours.

One purpose of calcination of the catalyst precursor is to obtain anoxide of the metal components. The catalyst precursor may be calcined ata temperature of 200–600° C. for 1–12 hours. Calcination may be in twostages, one at a temperature of 150–400° C. for 1–5 hours and another ata temperature of 400–600° C. for 4–8 hours with a temperature ramp of1–20° C./min, or of 5–10° C./min. In an embodiment of the invention fora two-stage calcination, the first is at a temperature of 290–310° C.for 2 hours and second at a temperature of 460–500° C. for 6 hours.Denitrification may occur in the first step. In the alternative,calcination is in one stage by increasing the temperature from ambienttemperature to about 485° C. over two hours instead of an initial stepor denitrification. Calcination may be done in a high temperature ovenor kiln.

The catalyst may be processed by sieving, forming and other means knownin the art to obtain catalyst particles of a certain size. Desiredparticle size and particle size distribution are related to the designof the reactor (size, shape, configuration, etc.), to the pressure dropintended for the process and to the process flow. For a two stagecalcination, the catalyst may be sieved or formed after the first stagecalcination and before the second stage calcination. In a commercialprocess the catalyst precursor may be sieved and formed after spraydrying and before calcination.

The X-ray diffraction pattern of the mixed metal oxide compounds isdescriptive of the catalyst made by the process of the presentinvention. The catalyst compositions of the Examples above have acharacteristic X-ray diffraction having diffraction peaks at thediffraction angles of 2θ, measured by using Cu Kα radiation, at 25.5,26.6 and 28.0 (+/−0.1°). There may be several additional diffractionpeaks present in a catalyst composition of the present invention butthese peaks will normally be evident.

The catalyst of the present invention may be used as an unsupportedcatalyst or a supported catalyst. The surface area of an unsupportedcatalyst is from 0.1 to 150 m²/g or from 1 to 20 m²/g. If supported, thesupport should be an inert solid which is chemically unreactive with anyof the active components of the catalyst and in one embodiment of theinvention is silica, alumina, niobia, titania, zirconia or mixturesthereof. The catalyst may be affixed to the support by methods known inthe art, including incipient wetness, slurried reactions and spraydrying. The catalyst, supported or unsupported, is not limited by shape,size or particle distribution and may be formed as appropriate for thereaction vessel in the process. Examples are powder, granules, spheres,cylinders, saddles, etc.

The catalyst is used in the gas phase catalytic oxidation of a feedstockgas comprising an olefin, such as propylene or isobutylene, with amolecular oxygen-containing gas, such as oxygen, to produce an aldehyde,such as acrolein or methacrolein. Oxygen may be supplied in the pureform or in an oxygen-containing gas, such as air or as an oxygen-diluentgas mixture. The diluent gas may be nitrogen, a hydrocarbon which isgaseous under the process conditions or carbon dioxide. Water and/or aninert gas, such as nitrogen, may also be present. In one embodiment ofthe invention, the reaction temperature is from 250–450° C. or from330–410° C. The reactor may be a fixed bed or a fluidized bed reactor.Reaction pressure may be from 0 to 100 psig or from 0 to 55 psig. Spacevelocity may be from 1000 to 12,500 hr⁻¹, 5000 to 10,000 hr⁻¹ or 7500 to10,000 hr⁻¹. Operating conditions will depend upon the specifics ofcatalyst performance and the economics of process design for theindividual process.

The invention having been generally described, the following examplesare given as particular embodiments of the invention and to demonstratethe practice and advantages thereof. It is understood that the examplesare given by way of illustration and are not intended to limit thespecification or the claims to follow in any manner.

EXAMPLE 1

43.57 g of ammonium paramolybdate and 1.65 g of ammonium paratungstatewere added into 87 ml of de-ionized water. The mixture was stirred andheated to 95° C. to form a solution.

A second solution was prepared by adding 1.3 ml of 70% nitric acid to9.3 ml of de-ionized water. 9.98 g of bismuth nitrate was dissolved inthe nitric acid solution. To this solution was added 19.94 g of ferricnitrate, 23.92 g nickel nitrate, 12.03 g of cobalt nitrate, 2.64 g ofmagnesium nitrate, 3.24 g of zinc nitrate and 85.3 ml of de-ionizedwater.

The second solution was added to the first solution dropwise.Precipitates were formed during the addition which created a slurry.

2.41 g of cesium nitrate and 2.11 g of antimony oxide were added assolids to the slurry.

The slurry was aged for 10 hours at 80° C. while being stirred. Afteraging, the liquid was evaporated at 100° C. The solid was dried at 120°C. for 3 hours. The dried solid was calcined at 300° C. for 2 hours inflowing air. The calcined solid was sieved to a mesh size of 20–30. Thesieved solid was calcined at 500° C. for 6 hours in flowing air. Acatalyst of the following composition was obtained:Mo₁₂Bi_(1.0)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

EXAMPLE 2

The procedure of Example 1 was repeated with the following amounts:

First Solution:

-   ammonium paramolybdate—45.84 g-   ammonium paratungstate—1.72 g    Second Solution:-   bismuth nitrate—5.19 g-   ferric nitrate—20.78 g-   nickel nitrate—24.92 g-   cobalt nitrate—12.53 g-   magnesium nitrate—2.75 g-   zinc nitrate—3.37 g    Slurry Addition:-   cesium nitrate—2.51 g-   antimony oxide—2.20 g

The composition of the catalyst wasMo₁₂Bi_(0.5)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

EXAMPLE 3

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—42.31 g-   ammonium paratungstate—1.61 g    Second Solution:-   bismuth nitrate—11.63 g-   ferric nitrate—23.40 g-   nickel nitrate—23.23 g-   cobalt nitrate—11.68 g-   magnesium nitrate—2.56 g-   zinc nitrate—3.14 g    Slurry Addition:-   cesium nitrate—2.34 g-   antimony oxide—2.05 g

The composition of the catalyst wasM₁₂Bi_(1.2)W_(0.3)Fe_(2.9)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

EXAMPLE 4

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—45.01 g-   ammonium paratungstate—0.00 g    Second Solution:-   bismuth nitrate—9.99 g-   ferric nitrate—19.90 g-   nickel nitrate—36.00 g-   cobalt nitrate—0.00 g-   magnesium nitrate—5.21 g-   zinc nitrate—0.00 g    Slurry Addition:-   cesium nitrate—2.42 g-   antimony oxide—2.12 g

The ammonium molybdate solution was heated to 95° C. over 45 minutesbefore the second solution was added and the catalyst precursor washeated to 485° C. with a 10° C./min ramp. The composition of thecatalyst was Mo_(12.3)Bi_(1.0)Fe_(2.4)Ni_(6.0)Sb_(0.7)Cs_(0.6)Mg_(1.0).

EXAMPLE 5

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—44.63 g-   ammonium paratungstate—0.00 g    Second Solution:-   bismuth nitrate—10.22 g-   ferric nitrate—20.43 g-   nickel nitrate—24.51 g-   cobalt nitrate—12.33 g-   magnesium nitrate—2.70 g-   zinc nitrate—3.32 g    Slurry Addition:-   cesium nitrate—2.47 g-   antimony oxide—2.17 g

The composition of the catalyst wasM₁₂Bi_(1.0)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

EXAMPLE 6

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—44.70 g-   ammonium paratungstate—0.00 g    Second Solution:-   bismuth nitrate—9.98 g-   ferric nitrate—19.94 g-   nickel nitrate—23.93 g-   cobalt nitrate—12.03 g-   magnesium nitrate—2.64 g-   zinc nitrate—3.24 g    Slurry Addition:-   cesiun nitrate—2.41 g-   antimony oxide—2.12 g

The composition of the catalyst wasMo_(12.3)Bi_(1.0)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 1

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—46.35 g-   ammonium paratungstate—1.76 g    Second Solution:-   bismuth nitrate—2.65 g-   ferric nitrate—21.21 g-   nickel nitrate—25.45 g-   cobalt nitrate—12.80 g-   magnesium nitrate—2.81 g-   zinc nitrate—3.45 g    Slurry Addition:-   cesium nitrate—2.56 g-   antimony oxide—2.25 g

The composition of the catalyst wasM₁₂Bi_(0.25)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 2

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—41.90 g-   ammonium paratungstate—1.59 g    Second Solution:-   bismuth nitrate—14.39 g-   ferric nitrate—19.18 g-   nickel nitrate—23.00 g-   cobalt nitrate—11.57 g-   magnesium nitrate—2.53 g-   zinc nitrate—3.12 g    Slurry Addition:-   cesium nitrate—2.31 g-   antimony oxide—2.05 g

The composition of the catalyst wasMo₁₂Bi_(1.5)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 3

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—42.43 g-   ammonium paratungstate—1.61 g    Second Solution:-   bismuth nitrate—9.70 g-   ferric nitrate—19.38 g-   nickel nitrate—11.63 g-   cobalt nitrate—23.38 g-   magnesium nitrate—2.57 g-   zinc nitrate—3.15 g    Slurry Addition:-   cesium nitrate—4.69 g-   antimony oxide—2.05 g

The composition of the catalyst wasMo₁₂Bi_(1.0)W_(0.3)Fe_(2.4)Co_(4.0)Ni_(2.0)Sb_(0.7)Cs_(1.2)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 4

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—44.33 g-   ammonium paratungstate—1.68 g    Second Solution:-   bismuth nitrate—8.12 g-   ferric nitrate—16.91 g-   nickel nitrate—24.34 g-   cobalt nitrate—12.24 g-   magnesium nitrate—2.68 g-   zinc nitrate—3.30 g    Slurry Addition:-   cesium nitrate—3.27 g-   antimony oxide—2.15 g

The composition of the catalyst wasMo₁₂Bi_(0.8)W_(0.3)Fe_(2.0)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.8)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 5

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—40.92 g-   ammonium paratungstate—1.55 g    Second Solution:-   bismuth nitrate—11.24 g-   ferric nitrate—22.63 g-   nickel nitrate—22.47 g-   cobalt nitrate—11.30 g-   magnesium nitrate—2.48 g-   zinc nitrate—3.04 g    Slurry Addition:-   cesium nitrate—1.88 g-   antimony oxide—4.25 g

The composition of the catalyst wasMo₁₂Bi_(1.2)W_(0.3)Fe_(2.9)Co_(2.0)Ni_(4.0)Sb_(1.5)Cs_(0.5)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 6

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—45.05 g-   ammonium paratungstate—1.71 g    Second Solution:-   bismuth nitrate—10.32 g-   ferric nitrate—10.31 g-   nickel nitrate—24.73 g-   cobalt nitrate—12.44 g-   magnesium nitrate—2.73 g-   zinc nitrate—3.35 g    Slurry Addition:-   cesium nitrate—2.49 g-   antimony oxide—2.18 g

The composition of the catalyst wasMo₁₂Bi_(1.0)W_(0.3)Fe_(1.2)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 7

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—54.46 g-   ammonium paratungstate—1.65 g    Second Solution:-   bismuth nitrate—9.98 g-   ferric nitrate—19.94 g-   nickel nitrate—23.92 g-   cobalt nitrate—12.03 g-   magnesium nitrate—2.64 g-   zinc nitrate—3.24 g    Slurry Addition:-   cesium nitrate—2.41 g-   antimony oxide—2.11 g

The composition of the catalyst wasMo₁₅Bi_(1.0)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 8

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—32.67 g-   ammonium paratungstate—1.65 g    Second Solution:-   bismuth nitrate—9.98-   ferric nitrate—19.94 g-   nickel nitrate—23.92 g-   cobalt nitrate—12.03 g-   magnesium nitrate—2.64 g-   zinc nitrate—3.24 g    Slurry Addition:-   cesium nitrate—2.41 g-   antimony oxide—2.11 g

The composition of the catalyst wasMo₉Bi_(1.0)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 9

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—45.52 g-   ammonium paratungstate—1.73 g    Second Solution:-   bismuth nitrate—6.25 g-   ferric nitrate—17.36 g-   nickel nitrate—25.00 g-   cobalt nitrate—12.57g-   magnesium nitrate—2.76 g-   zinc nitrate—3.38 g    Slurry Addition:-   cesium nitrate—2.52 g-   antimony oxide—2.21 g

The composition of the catalyst wasMo₁₂Bi_(0.6)W_(0.3)Fe_(2.0)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 10

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—30.35 g-   ammonium paratungstate—1.15 g    Second Solution:-   bismuth nitrate—4.17 g-   ferric nitrate—11.57 g-   nickel nitrate—14.78 g-   cobalt nitrate—10.26 g-   magnesium nitrate—1.84 g-   zinc nitrate—2.26 g    Slurry Addition:-   cesium nitrate—1.68 g-   antimony oxide—1.47 g

The composition of the catalyst wasMo₁₂Bi_(0.6)W_(0.3)Fe_(2.0)Co_(2.4)Ni_(3.6)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

For each of the catalysts from the Examples and Comparative Examplesabove, 1.0–2.0 cc of catalyst were mixed with quartz chips to make atotal volume of 5 cc, which were placed into a downflow reactor havingan internal diameter of 0.25 inches. A gas consisting of 3.6%isobutylene, 8.6% oxygen, 28% water and the balance as nitrogen waspassed over the catalyst bed in the reactor. The volumetric flow rateswere varied between 38 and 85 sccm. The internal reactor temperature andpressure were maintained at 390° C. and 0 psig. The gas hourly spacevelocity was about 1500 to about 3400 hr⁻¹. The catalyst loading and gasflow rate were adjusted such that, where possible, a conversion between97 and 99% was obtained. Product liquid was condensed into a glass trapmaintained at 0° C. for a period of approximately three hours. Theyields of methacrylic acid and acetic acid were determined from thisliquid. The concentrations of isobutylene, methacrolein and otherbyproducts were determined from on-line analysis by gas chromatography.

Catalyst activities are reported in Table I relative to example 3, forwhich 1.5 cc of catalyst at a flow rate of 38 sccm gave 98.0% conversionand 87.4% selectivity to methacrolein. Repeated tests of the catalystsof the Examples suggest that the accuracy of the relative activitynumber is roughly ±0.05.

It is well known that selectivity for isobutylene oxidation (and indeedmost partial oxidation reactions) is dependent on isobutyleneconversion; as conversion is increased the selectivity decreases due tofurther oxidation of the desired products. Given this, the selectivitiesof two different catalysts must be compared at the same conversion forthe comparison to be meaningful. The selectivity of example 1 wasmeasured across a wide range of conversions, from less than 30% to morethan 99% and fit a curve to this data over that range. The actualselectivities of examples 2 through 6 and comparative examples 1 through10 were compared to the selectivity curve that was generated for thecatalyst of example 1 at the same conversion. The absolute percentdifference between the selectivities of the catalysts of examples 2through 6 and comparative examples 1 through 10 and the selectivity ofexample 1 at the same conversion is reported in Table I as “relativeselectivity.” The measurement error on the relative selectivity numberis roughly ±1. Mass balances were measured for every sample and averaged96%.

TABLE IMo₁₂Bi_(a)W_(b)Fe_(c)Co_(d)Ni_(e)Sb_(f)Cs_(g)Mg_(h)Zn_(i)P_(j)O_(x)(3a + 3c + 2d + 2e + g + 2h + 2i)/ RELATIVE RELATIVE EXAMPLE c/a c/g (2× 12 + 2b) ACTIVITY SELECTIVITY 1 2.4 4.0 1.01 1.09 Same 2 4.8 4.0 0.951.44 Same 3 2.4 4.8 1.09 1.00 — 4 2.4 4.0 1.06 1.01 Same 5 2.4 4.0 1.031.01 Same 6 2.4 4.0 1.0 1.34 +1 COMPARATIVE 1 9.6 4.0 0.92 1.97 −2COMPARATIVE 2 1.7 4.0 1.07 0.57 Same COMPARATIVE 3 2.4 2.0 1.03 0.39Same COMPARATIVE 4 2.5 2.5 0.94 0.84 −2 COMPARATIVE 5 2.4 5.8 1.09 1.27−5 COMPARATIVE 6 1.2 2.0 0.86 0.80 −2 COMPARATIVE 7 2.4 4.0 0.81 1.42 −3COMPARATIVE 8 2.4 4.0 1.33 0.12 −3 COMPARATIVE 9 3.3 3.3 0.91 0.90 SameCOMPARATIVE 10 3.3 3.3 0.91 0.96 Same

The above examples demonstrate the effectiveness of the relative amountratios of certain components to certain other components in a mixedmetal oxide catalyst for the catalytic oxidation of an olefin to anunsaturated aldehyde, e.g., propylene or isobutylene to acrolein ormethacrolein. Those catalysts which have ratios of iron to bismuth, ironto cesium and bismuth, iron, cobalt, nickel, cesium, magnesium and zincto molybdenum and tungsten which are within the ranges of 2.4–4.8,4.0–4.8, and 0.95–1.09, respectively, have activity better than andselectivity as good or better than those catalysts having any one ofthese ratios outside the ranges of 2–6, 3.3–5 and 0.95 to 1.1,respectively. The catalysts which have a ratio outside the ranges of2–6, 3.3–5 and 0.95 to 1.1, respectively, and have selectivity as goodas that of catalysts of the present invention (Comparative Examples 2,3, 9 and 10) have activity which is unsuitable for good catalystperformance (0.57, 0.39, 0.90, 0.96 relative activity). Those catalystswhich have ratios outside the ranges of 2–6, 3.3–5 and 0.9 to 1.1,respectively, and have activity higher than that of catalysts of thepresent invention (Comparative Examples 1, 5 and 7 at 1.97, 1.27 and1.42 relative activity) have selectivities which are unsuitable for goodcatalyst performance (−2, −5 and −3 relative selectivity).

EXAMPLE 7

The procedure of Example 1 was repeated.

The composition of the catalyst wasMo₁₂Bi_(1.0)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5).

COMPARATIVE EXAMPLE 11

The procedure of Example 1 was repeated except for the followingamounts:

First Solution:

-   ammonium paramolybdate—42.94 g-   ammonium paratungstate—1.63 g    Second Solution:-   bismuth nitrate—9.83 g-   ferric nitrate—19.65 g-   nickel nitrate—23.58 g-   cobalt nitrate—11.85 g-   magnesium nitrate—2.60 g-   zinc nitrate—3.19 g    Slurry Addition:-   thallium nitrate—3.24 g-   antimony oxide—2.08 g

The composition of the catalyst wasM₁₂Bi_(1.0)W_(0.3)Fe_(2.4)Co_(2.0)Ni_(4.0)Sb_(0.7)Tl_(0.6)Mg_(0.5)Zn_(0.5).

For each of the catalysts from the Examples and Comparative Examplesabove, 1.5 cc of catalyst were mixed with quartz chips to make a totalvolume of 5 cc, which were placed into a downflow reactor having aninternal diameter of 0.25 inches. A gas consisting of 3.6% isobutylene,8.6% oxygen, 28% water and the balance as nitrogen was passed over thecatalyst bed in the reactor. The volumetric flow rates were about 250sccm. The internal reactor temperature and pressure were maintained at380° C. and 55 psig. The gas hourly space velocity was about 10,000hr⁻¹. The concentrations of isobutylene, methacrolein and otherbyproducts were determined from on-line analysis by gas chromatography.

Catalyst activities are reported in Table II relative to example 7, forwhich 1.5 cc of catalyst at a flow rate of 250 sccm gave 80.0%conversion and 87.4% selectivity to methacrolein. Example 7 is definedto have relative activity of 1.0 and relative selectivity of zero.

TABLE II RELATIVE RELATIVE EXAMPLE Cs Tl ACTIVITY SELECTIVITY 7 0.6 0.01.0 — COMPARATIVE 11 0.0 0.6 2.8 −12

The above examples demonstrate the effectiveness of the presence ofcesium relative to certain other components. i.e., thallium, in a mixedmetal oxide catalyst for the catalytic oxidation of an olefin to anunsaturated aldehyde, e.g., propylene or isobutylene to acrolein ormethacrolein. While the activity of the catalyst containing thallium ishigher than that of the catalyst containing cesium, the selectivity issignificantly lower.

EXAMPLE 8

The catalyst of Example 3(Mo₁₂Bi_(1.2)W_(0.3)Fe_(2.9)Co_(2.0)Ni_(4.0)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5))was tested per the conditions below.

COMPARATIVE EXAMPLE 12

The catalyst of Comparative Example 10(Mo₁₂Bi_(0.6)W_(0.3)Fe_(2.0)Co_(2.4)Ni_(3.6)Sb_(0.7)Cs_(0.6)Mg_(0.5)Zn_(0.5))was tested per the conditions below.

For each of the catalysts from Example 8 and Comparative Example 12above, 1.5 cc of catalyst were mixed with quartz chips to make a totalvolume of 5 cc, which were placed into a downflow reactor having aninternal diameter of 0.25 inches. A gas consisting of 3.6% isobutylene,8.6% oxygen, 28% water and the balance as nitrogen was passed over thecatalyst bed in the reactor. The volumetric flow rates were about 250sccm. The internal reactor temperature and pressure were maintained at370° C. and 55 psig. The gas hourly space velocity was about 10,000hr⁻¹. The concentrations of isobutylene, methacrolein and otherbyproducts were determined from on-line analysis by gas chromatography.

Catalyst activities are reported in Table III relative to Example 8, forwhich 1.5 cc of catalyst at a flow rate of 250 sccm gave 94.8%conversion and 81% selectivity to methacrolein.

TABLE III RELATIVE RELATIVE EXAMPLE ACTIVITY SELECTIVITY 8 1.00 —COMPARATIVE 12 0.96 −2

Better selectivity was obtained with the catalyst of Example 8 than forthe catalyst of Comparative Example 12 at a gas hourly space velocity ofabout 10,000 hr⁻¹ and a pressure of 55 psig while the same catalysts(Example 3 and Comparative Example 10) have approximately the sameselectivity at a gas hourly space velocity of about 1500 to about 3400hr⁻¹ and a pressure of 0 psig. Commercial operation will require highergas hourly space velocities of 7500 to 12,500 hr⁻¹ due to the pressuredrop across the reactor and the pressure head needed to push reactantsand products downstream. Therefore, the catalysts of the presentinvention will perform better under commercial conditions than catalystsnot having the claimed relative amount ratios of cesium to bismuth, ofiron to bismuth and of bismuth, iron, cesium and certain other metals tomolybdenum and, optionally, tungsten.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A catalyst for the oxidation of an olefin to an unsaturated aldehydecomprising a mixed metal oxide having the formula:Mo₁₂Bi_(a)W_(b)Fe_(c)Cs_(g)M_(m)O_(x) wherein a is in the range from 0.1to 1.5, b is in the range from 0 to 9, c is in the range from 0.2 to5.0, g is in the range from 0.1 to 1.5, M is one or more selected fromthe group consisting of calcium, strontium, lithium, sodium, selenium,cobalt, nickel, magnesium, zinc, potassium, rubidium, thallium,manganese, barium, chromium, tin, lead, cadmium and copper, m is in therange from 0 to 9, x is determined by the valences of the othercomponents and wherein the relative amount ratio of c to g is from 3.3to 5.0, the relative amount ratio of c to a is from 2.0 to 6.0 and therelative amount ratio of (3a+3c+g+Σv_(n)m_(n))/(2×12+2b) is from 0.95 to1.10 with v being valence of each M, and n being the total number of M.2. The catalyst of claim 1 wherein g is in the range from 0.4 to 1.5. 3.The catalyst of claim 1 wherein the mixed metal oxide is having theformula:M₁₂Bi_(a)W_(b)Fe_(c)Cs_(g)M_(m)M′_(m′)O_(x) wherein M′ is one or moreselected from the group consisting of cerium, antimony, phosphorus,boron, sulfur, silicon, aluminum, titanium, tellurium, vanadium,zirconium and niobium, m′ is in the range from 0 to
 9. 4. The catalystof claim 3 wherein the mixed metal oxide is of the formula:Mo₁₂Bi_(a)W_(b)Fe_(c)Co_(d)Ni_(e)Sb_(f)Cs_(g)Mg_(h)Zn_(i)P_(j)O_(x)wherein b is 0 to 4, d is 0 to 9, e is 0 to 9, f is 0 to 2.0, h is 0 to1.5, i is 0to 2.0, j is 0 to 0.5 and wherein the relative amount ratioof (3a+3c+2d+2e+g+2h+2i)/(2×12+2b) is from 0.95 to 1.10.
 5. The catalystof claim 4 wherein the relative amount ratio of c to a is from 2.4 to4.8, the relative amount ratio of c to g is from 4.0 to 4.8 and therelative amount ratio of (3a+3c+2d+2e+g+2h+2i)/(2×12+2b) is from 0.95 to1.09.
 6. The catalyst of claim 5 wherein the catalyst has an X-raydiffraction pattern of diffraction peaks at the diffraction angles of2θ, measured by using Cu Kα radiation, at 25.5, 26.6 and 28.0.
 7. Thecatalyst of claim 5 wherein the catalyst is unsupported and has asurface area of from 0.1 to 150 m²/g.
 8. The catalyst of claim 7 whereinthe catalyst has a surface area of from 1 to 20 m²/g.
 9. The catalyst ofclaim 1 wherein the mixed metal oxide is supported on an inert support.10. The catalyst of claim 9 wherein the inert support is silica,alumina, niobia, titania, zirconia or mixtures thereof.
 11. The catalystof claim 1 wherein the catalyst is in the form of powder, granules,spheres, cylinders or saddles.